bpo-38724: Implement subprocess.Popen.__repr__ (GH-17151)

Lib/subprocess.py

@@ -978,6 +978,15 @@ class Popen(object):
 
             raise
 
+    def __repr__(self):
+        obj_repr = (
+            f"<{self.__class__.__name__}: "
+            f"returncode: {self.returncode} args: {list(self.args)!r}>"
+        )
+        if len(obj_repr) > 80:
+            obj_repr = obj_repr[:76] + "...>"
+        return obj_repr
+
     @property
     def universal_newlines(self):
         # universal_newlines as retained as an alias of text_mode for API

Lib/test/test_subprocess.py

@@ -1360,6 +1360,30 @@ class ProcessTestCase(BaseTestCase):
         self.addCleanup(p.stdin.close)
         p.communicate(b"x" * 2**20)
 
+    def test_repr(self):
+        # Run a command that waits for user input, to check the repr() of
+        # a Proc object while and after the sub-process runs.
+        code = 'import sys; input(); sys.exit(57)'
+        cmd = [sys.executable, '-c', code]
+        result = "<Popen: returncode: {}"
+
+        with subprocess.Popen(
+                cmd, stdin=subprocess.PIPE, universal_newlines=True) as proc:
+            self.assertIsNone(proc.returncode)
+            self.assertTrue(
+                repr(proc).startswith(result.format(proc.returncode)) and
+                repr(proc).endswith('>')
+            )
+
+            proc.communicate(input='exit...\n')
+            proc.wait()
+
+            self.assertIsNotNone(proc.returncode)
+            self.assertTrue(
+                repr(proc).startswith(result.format(proc.returncode)) and
+                repr(proc).endswith('>')
+            )
+
     def test_communicate_epipe_only_stdin(self):
         # Issue 10963: communicate() should hide EPIPE
         p = subprocess.Popen(ZERO_RETURN_CMD,

Misc/NEWS.d/next/Library/2019-11-14-14-13-29.bpo-38724.T5ySfR.rst

@@ -0,0 +1 @@
+Add a repr for ``subprocess.Popen`` objects. Patch by Andrey Doroschenko.